The present invention relates to reciprocating power saws and more specifically to a clamping system that permits the quick and easy removal and replacement of the blade. An inherent problem with reciprocating saws is that the blade of the saw quickly becomes dull and/or breaks requiring frequent blade changes. Prior art blade assemblies typically require a tool, such as a screwdriver or Allen wrench to change the blade. This is a slow and at times difficult process. Moreover, at times the required tool may not be available having been misplaced or lost. To address these problems a number of prior art designs use a blade clamp which does not require a tool.
For example, U.S. Pat. No. 3,583,716 discloses one such tool-less assembly for attaching and locking the saw blade in place. The shank of the saw blade is received within a slot in a saw bar which is driven by a motor. An aperture is provided in the shank of the blade. An aperture is likewise provided in the saw bar in communication with the slot receiving the blade shank. A ball is mounted in and freely removable within the aperture in the saw bar. A collar is mounted on the saw bar and is freely rotatable about the saw bar. The collar has an eccentrically grooved surface functioning as a cam surface engaging the ball. When the blade is inserted into the saw bar the collar is rotated to shift the ball to contact the aperture in the shank of the blade. In this position the blade is locked in place until the collar is rotated to an unlocked position. In order to stabilize the blade within the saw bar a pin is provided in the saw bar extending into the longitudinal slot. The shank of the saw blade is provided with a notch or recess which receives the pin seating the saw blade within the saw bar.
U.S. Pat. No. 3,823,473 also discloses a tool-less attachment means for a saber saw. The patent describes several embodiments of an attachment assembly where pins or balls engage the shank of a blade to secure the blade in place.
U.S. Pat. No. 3,927,893 also discloses an assembly adapted to engage the blade of a reciprocating tool and secure the blade in position. This apparatus includes a ball which is selectively engaged with a recess or dimple in a blade to seat the blade firmly in the assembly.
While these prior art patents describe a blade clamp assembly which does not require the use of a tool, each requires the use of a blade with a shank specifically designed for the patented structure. For example, in U.S. Pat. No. 3,583,716 the shank of the blade is provided with a notch that engages a pin in the tool bar to seat and stabilize the saw in the saw bar. Manufacturers of blades for reciprocating saws have standardized the width and length of the shank of the blade and the position of the aperture or hole in the shank. It is desirable for the power saw to accept blades having the standardized dimensions and configurations. The user of the saw is thus not limited in his ability to obtain acceptable replacement blades.
Thus, the design of the present invention was developed to provide a tool-less clamp assembly for a reciprocating saw which does not require a unique shank design but, on the other hand, will accept the standardized and universal shank design of many blade manufacturers.
In addition the attachment means for the saw blade must stabilize the blade and prevent movement of the blade when it is locked in the operative position. The prior art discloses a number of different such stabilization means. As mentioned, U.S. Pat. No. 3,583,716, for example, discloses a pin that is received in a recess in the shank of the blade. U.S. Pat. No. 5,103,565 discloses in one embodiment a blade holder for receiving a universal type blade where a pin is designed to engage a radiused surface on the shank. Despite the fact that such universal blades are standard in many respects, one cannot always rely upon the radiused surface engaged by the pin of the '565 patent to be in a standard location. It can be seen that these prior art patents disclose additional mechanical elements such as pins in order to stabilize the saw blade.
Accordingly, the present invention is also directed toward a clamp assembly which will affect blade stabilization without complex and unnecessary hardware designs.